Sinead O’Connor posted an open letter on her website, expressing her strong feelings about the case of Trayvon Martin, the Florida teen shot and killed in February by a neighborhood watch volunteer.

In the lengthy post, the outspoken Irish singer/songwriter is outraged that George Zimmerman, who claims he shot Martin in self-defense, has not been arrested. She writes:

“I would like to extend my very deepest sympathies to the family and other loved ones of murdered teenager, Treyvon Martin. I am very sad today (and am certain the whole of Ireland is) to learn of poor Treyvon’s terrifying ordeal and horrified by the fact his known and named and admitted killer has not been arrested, despite the crime having taken place a month ago. This is a disgrace to the entire human race.”

Several other celebrities including Sean “P. Diddy” Combs, Spike Lee and members of the NBA’s Miami Heat have all expressed their concern and support for Martin’s family.